1. Technical Field
The present invention relates to optical measurement devices, in particular, to an optical system arranged in an optical measurement device.
2. Related Art
A sensor device for measuring displacement, length, angle, and the like of various measuring target objects is conventionally known. For instance, the optical measurement device (also referred to as “displacement sensor”) that uses a light cutting method is known, the optical measurement device including a light projection unit for shaping a light from a light source to a line beam, and irradiating a surface of a measuring target object with the light at a predetermined angle, a photographing unit for photographing a line beam irradiating position at the surface of the measuring target object using a two-dimensional imaging element from a direction different from the irradiating direction of the line beam and acquiring an image including a sectional contour image of a light cutting surface, and a measurement unit for generating a measurement value and/or determination value by executing a predetermined measurement process based on the sectional contour image of the light cutting surface obtained by the photographing unit.
The above-described optical measurement device measures the displacement by applying the principle of triangulation, which optical measurement device can be broadly divided into two types according to the type of reflected light from a measuring target region received by the imaging unit. One type is a method of directly receiving a specular reflected light from an object, and the other type is a method of projecting a projection beam perpendicularly to the measurement surface and receiving a diffuse reflected light in the reflected light.
The direction of a line formed by the cross-section of the line beam corresponds to a vertical scanning direction (or horizontal scanning direction) in the view of the two-dimensional photographing element. The direction the sectional contour image-formed by the line beam moves in the view of the two-dimensional imaging element when the distance between the measurement device (generally sensor head) and the measuring target object changes corresponds to the horizontal scanning direction (or vertical scanning direction). The sectional contour image of the light cutting surface is thereby formed at the light receiving surface of the two-dimensional imaging element.
According to such optical measurement device, since the line beam having a linear cross-section is used for a cutting light, the information of a series of measurement points along a constant line at the surface of the measuring target object can be collectively acquired without relatively moving the cutting light and the measuring target object, as a device using a spot light having a dotted cross-section for the cutting light. Thus, if applied to tests etc. of industrial products flowing through the production line, the dimension of each portion of the surface of the measuring target object can be accurately measured based on the information of the series of measurement points, and defect determination of the product and the like can be rapidly and reliably carried out.
In tests etc. of industrial product of this type, the measuring target object having various shapes needs to be considered. For instance, in some industrial products, the reflected light quantity the sensor can retrieve partially differs since one part of the surface is an inclined surface or a curved surface. When testing such industrial products (measurement of surface displacement etc.), the image becomes dark due to lack of reflected light quantity or normal measurement may not be performed as light cannot be retrieved.
Japanese Patent Publication No. 3575693 (patent document 1) discloses an optical measurement device which synthesizes a plurality of images having different photographing conditions and performs measurement based on the synthesized image to solve the above problems.